1 Technical Field
The present invention relates to stators for rotating electric machines that are used in, for example, motor vehicles as electric motors and electric generators.
2 Description of Related Art
There are known rotating electric machines that are used in motor vehicles as electric motors and electric generators. These rotating electric machines generally include a rotor and a stator. The rotor is rotatably supported by a housing. The stator includes an annular stator core and a three-phase stator coil. The stator core is disposed in radial opposition to the rotor and has a plurality of slots arranged in a circumferential direction thereof. The stator coil is comprised of a plurality of phase windings that are mounted on the stator core so as to be received in the slots of the stator core. The stator coil has a pair of annular coil end parts that protrude axially outward respectively from an opposite pair of axial end faces of the stator core.
Moreover, there is disclosed an arrangement of lead wires in Japanese Patent No. JP5647285B2 and Japanese Patent Application Publication No. JP2009011116A (to be respectively referred to as Patent Documents 1 and 2 hereinafter). Specifically, according to the disclosure of Patent Documents 1 and 2, lead wires, such as input wires, output wires and neutral wires of the stator coil, are led out from a radially inner periphery of one of the coil end parts of the stator coil, arranged to extend across the coil end part to the radially outside of the coil end part and joined to other corresponding electric conductor wires on the radially outside of the coil end part.
However, the above arrangement of the lead wires disclosed in Patent Documents 1 and 2 has the following problems.
That is, since the lead wires, which are led out from the radially inner periphery of the coil end part, are arranged to extend across the coil end part to the radially outside of the coil end part, the extending lengths of the lead wires from the radially inner periphery of the coil end part to the corresponding electric conductor wires become large. Consequently, the weights of the lead wires are increased. Moreover, since the lead wires are arranged to hang over the coil end part, the rigidities of the lead wires are lowered. As a result, the natural frequencies of the lead wires are lowered. When the natural frequencies are low, the lead wires may resonate with vibration accompanying rotation of a vehicle engine; thus excessive stress may be induced in joints where the lead wires are jointed to the corresponding electric conductor wires, resulting in failure (e.g., breakage or disconnection) of the joints.